1. Field of the Invention
The present invention relates to a pump and more particularly to an improvement in the inlet valve of the pump as well as to a process for manufacturing such a pump.
2. Related Art
The invention concerns pumps of the type comprising in particular a substantially cylindrical body in one-piece, provided in its lower part with a port for admission of the product and with a valve. This valve is constituted in known manner by a cavity forming seat and containing an element capable of moving between a lower stop corresponding to a position of obturation of the admission port and an upper stop corresponding to the opening of said port and to the filling of the pump body by the product.
The stroke of the mobile element which is generally constituted by a ball, must be adjusted so as to obtain the regular delivery by the pump of identical, constant doses.
Consequently, the upper and lower stops must be positioned with precision.
According to a known solution, the upper stop is constituted by the lower turn of a helicoidal return spring housed in the pump body.
However, this spring creates problems of bulk and/or of compatibility with the product.
A variant embodiment of this upper stop consists in fixing an added piece in the lower part of the pump body above the mobile element.
However, the production of this piece and its assembly in the pump are complex and expensive operations.
In addition, it is necessary to arrange on the pump body specific means for fixing this piece.
Another solution lies in the presence of retaining bosses moulded directly in the pump body like in U.S. Pat. No. 2,294,568.
These bosses project inside the pump body and define towards the top the cavity in which the mobile element is housed.
However, the transverse dimension of these bosses measured from the inner wall of the body always remains small with respect to the inner diameter of the cavity in order to allow unmoulding of the body and the subsequent introduction of the mobile element in the cavity. For the same reasons, the section of these retaining bosses comprises neither angular zone nor free edge in undercut. Nonetheless, despite this, the projecting bosses are sometimes crushed upon ejection from the mould, which considerably compromises the subsequent reliability of the pump insofar as the mobile element can then escape from its cavity.
In the Patent Abstracts of Japan Vol. 15 No. 392 of Oct. 4, 1991 and JP-A-316 1066, the upper stop of the mobile element of the valve is ensured by means of discontinuous internal projections performed by cut-out using a tool incorporating a blade whose profile is bevelled.
Moreover, the non-aggressive profile of these projections promotes the jamming of the mobile element in the top of the cavity, which increases the risks of dysfunction of the pump.
All these problems are even more substantial when the pump is a miniature pump, intended for example for samples of perfume or dispensers of small doses of medicaments.
It is an object of the present invention satisfactorily to solve the technical problems raised by the prior art.
This object is attained in accordance with the invention by a pump of the type comprising in particular a substantially cylindrical body in one piece provided, in its lower part, with a port for admission of the product and with a valve constituted by a cavity containing an element capable of moving between a lower stop corresponding to the obturation of said admission port and an upper stop corresponding to the opening of said port, wherein said upper stop is formed by at least one discontinuous internal projection whose transverse dimension measured in the cavity is at least equal to 20% of the largest transverse dimension of the mobile element.
According to an advantageous characteristic, said projection has an inner edge of which the generatrices are substantially parallel to the axis of the body.
Diameter is included between 50% and 90% of the largest transverse dimension of the mobile element.
According to other characteristics, the upper face of said projection is wider than its lower face.
Said projection preferably presents, outside said cavity, an at least partly cylindrical cut out of which the generatrices are parallel to the axis of the body.
According to a particular embodiment, the upper stop comprises four projections diametrally opposite in two""s.
These four projections are preferably separated by free sectors capable of allowing the product to pass.
According to a specific variant, the free sectors have an angular length included between 30xc2x0 and 80xc2x0.
Another object of the invention is a process for manufacturing a pump, characterized in that the pump body is produced, then at least one discontinuous internal projection is formed by fashioning the inner wall of said body by means of a punching die, of which the diameter of the head is included between 110% and 140% of the largest transverse dimensions of the mobile element.
The transverse dimension of the internal projection, the diameter of the upper orifice of the cavity as well as the diameter of the head of the punching die are parameters which are chosen with reference to the largest transverse dimension of the mobile element but which also depend on the depth of penetration of the punching die in the wall of the body of the pump. This depth is limited by the available wall thickness in the zone intended for fashioning and, for determining the values of the above parameters, was fixed at 25% of the wall thickness of the pump body.
According to an advantageous characteristic, said body is fashioned internally by the punching die pushing the matter constituting the wall downwardly and inwardly, so as partly to close the cavity.
According to another characteristic, said body is fashioned internally with a punching die incorporating four blades diametrally opposite in two""s.
According to yet another characteristic of the process, the mobile element is introduced in the lower part of the body, prior to the formation of said internal projection.
The pump of the invention thus comprises a particularly reliable and precise inlet valve. With such a valve, the risks of the mobile element jamming or escaping are virtually non-existent.
In addition, the process of the invention makes it possible to produce projections whose transverse dimension is so large that they could not be made by moulding and which, moreover, would not allow the subsequent positioning of the mobile element.
The process of the invention also enables projections of various dimensions to be made on the same type of pump body, which allows mobile elements of different sizes to be used.